1. Technical Field
The present invention relates to a fiber holder and a fiber laser apparatus and, particularly, to a configuration of a fiber holder for winding an optical fiber and fixing the same.
2. Related Art
A laser processing apparatus, typically a laser marking apparatus, a welding apparatus, and a trimming apparatus, is generally configured by a laser oscillator, a driver for driving the laser oscillator, a power source for the driver, and a control board for controlling the laser. In recent years, in such a laser processing apparatus, a conventional solid state laser is progressively being replaced with a fiber laser in view of its advantages, such as a high efficiency, a high stability, and a high beam quality.
In a general fiber laser, a laser beam is amplified by a rare-earth doped fiber. In order to obtain a laser beam having a high power, the rare-earth doped fiber is required to have a certain amount of length. Therefore, configurations for accommodating optical fibers have been proposed so far.
For example, U.S. Unexamined Patent Publication No. 2008/0267575A1 (Patent Literature 1) discloses a bobbin having a circular shape which is formed by metal, such as aluminum or copper. On the side face of this bobbin, a helical groove is formed for accommodating an optical fiber. Moreover, Japanese Unexamined Patent Publication No. 2008-244483 (Patent Literature 2) discloses an optical fiber holding device in which a helical groove for accommodating an optical fiber is formed on a plain surface.
A general optical fiber used for a fiber laser is very thin, such as about 250 to 1000 μm. Particularly, in a rare-earth doped fiber, in order to perform an optical amplification and a laser oscillation, a laser beam having a high power is transmitted through the rare-earth doped fiber. When the rare-earth doped fiber is damaged, a laser beam leaks through the damaged portion, thereby, a problem of heat generation at the fiber, or heat generation at a fiber coating etc. may be caused. Accordingly, fibers should be treated very carefully.
On the other hand, in the bobbin disclosed in Patent Literature 1, a helical groove is formed on its side face. As the optical fiber becomes longer, the vertical length of the bobbin (i.e., the center axis direction of the helical groove) should be made longer. Accordingly, it is difficult to realize a compact optical fiber holder by the bobbin disclosed in Patent Literature 1. Moreover, it is difficult for the bobbin disclosed in Patent Literature 1 to visually confirm the state in which a fiber is wound. Therefore, when a part of the fiber is deviated from the groove, it would be possible to overlook the portion.
On the other hand, in the fiber holding device disclosed in Patent Literature 2, an optical fiber is held in a helical groove formed on a plain surface. However, a method for accommodating the optical fiber in the groove, i.e., a method for winding the optical fiber, is not concretely disclosed in Patent Literature 2.